Critical Appraisal of Article Critical Appraisal of Article on Prognosison Prognosis

Dr. Faisal Al HaddadConsultant of Occupational Health & Family MedicinePSMMC

11 . .Was there Was there a representative and a representative and well-defined sample of patients well-defined sample of patients at a at a similar point in the course of the similar point in the course of the diseasedisease??

The authors should describe and specify their criteria for establishing that the patient has the disorder of interest (well-defined sample of patients)

and how they selected their patient sample

(representative). Selection bias: Patients from tertiary referral

centres may have more advanced disease and poorer prognoses than patients from primary care.

11 . .Was there a representative and Was there a representative and well-defined sample of patients well-defined sample of patients at a at a similar point in the course of the similar point in the course of the diseasedisease??

Authors should provide a clear description of the stage of disease at which patients entered the study.

It is preferable if study patients are enrolled at a uniformly early time in the disease, usually when the disease first becomes manifest. Such groups of patients are called an ‘inception cohort’.

22 . .Was follow-up sufficiently long Was follow-up sufficiently long and completeand complete??

Investigators must follow patients for long enough to detect the outcomes of interest.

Patients may fail to return because they have suffered exactly those events in which the investigators are interested.

Conversely, patients who feel entirely healthy may also be less likely to return for evaluation because they feel so well.

The greater the no. of patients lost to FU, the less accurate the estimate regarding the risk of the adverse outcome.

22 . .Was follow-up sufficiently long Was follow-up sufficiently long and completeand complete??

The larger the number of patients whose fate is unknown relative to the number who have suffered an event, the greater the threat to the study's validity.

If the number of patients lost potentially jeopardizes the study's validity, you should: ◦ look for the reasons for patients being lost, ◦ and compare the important demographic and clinical

characteristics of the patients who were lost to the patients in whom follow-up was complete.

To the extent that the reasons for disappearance are unrelated to outcome, and the patients who are lost are similar to those for whom information is complete, you may feel reassured.

If investigators omit information about reasons for loss to follow-up, or the characteristics of the patients who are lost, the strength of inference from the study results will be weaker.

33 . .Were objective and unbiased Were objective and unbiased outcome criteria usedoutcome criteria used??

Investigators must provide a clear and sensible definition of adverse outcomes before the study starts.

Outcome events can vary from those that are objective and easily measured (death), to those which require some judgement (myocardial infarction), to those that require considerable judgement, and may often be difficult to measure (eg disability, quality of life).

To minimize bias, the individual determining the outcomes should not know whether the patient had a potential prognostic factor(blinding). This is not always possible, and for unequivocal events such as death may not be necessary.

Blinding is essential for outcomes requiring a great deal of judgement, such as transient ischemic attacks, or unstable angina.

44 . .Was there adjustment for Was there adjustment for important prognostic factorsimportant prognostic factors??

The study should adjust for known prognostic factors in the analysis so that results are not distorted.

Since treatments can also alter patient outcomes, they should be taken into account when analyzing prognostic factors. The investigators should adjust for differences in treatment in the analysis.

11 . .How large is the likelihood of the How large is the likelihood of the outcome event(s) in a specified outcome event(s) in a specified period of timeperiod of time??

RR, ARR

Survival Curve

22 . .How precise are the estimates of How precise are the estimates of likelihoodlikelihood??

After determining the size of the risk, we should next examine the precision of the estimate, which is best done with a confidence interval.

In most survival curves the earlier follow-up periods usually include results from more patients than the later periods (due to losses to follow-up).

This means that the survival curves are more precise in the earlier periods, indicated by narrower confidence bands around the left-hand parts of the curve.

11 . .Were the study patients similar Were the study patients similar to my ownto my own??

The authors should describe the study patients in enough detail to allow comparison with your patients.

The article should list the patients' important clinical characteristics, along with the definitions used for these characteristics.

The closer the match between the patient before you and those in the study, the more confident you can be in applying the study results to that patient.

22 . .Will the results lead directly to Will the results lead directly to selecting or avoiding therapyselecting or avoiding therapy??

Knowing the expected clinical course of your patient's

condition can help you judge whether treatment should

be offered or avoided.

33 . .Are the results useful for Are the results useful for reassuring or counselling patientsreassuring or counselling patients??

Even if the prognostic result does not lead you to prescribe an effective therapy, it can still be clinically useful.

A valid, precise and generalizable result of uniformly good prognosis is very helpful to the clinician when reassuring a concerned patient or relative.

On the other hand, a prognostic result of uniformly bad prognosis provides the clinician with a starting place for a discussion with the patient and family, leading to counselling about end-of-life concerns.